title: Proximal tubular hypertrophy and enlarged glomerular and proximal tubular urinary space in obese subjects with proteinuria.
abstract: BACKGROUND
  Obesity is associated with glomerular hyperfiltration, increased proximal tubular sodium reabsorption, glomerular enlargement and renal hypertrophy. A single experimental study reported an increased glomerular urinary space in obese dogs. Whether proximal tubular volume is increased in obese subjects and whether their glomerular and tubular urinary spaces are enlarged is unknown.
  
  
  OBJECTIVE
  To determine whether proximal tubules and glomerular and tubular urinary space are enlarged in obese subjects with proteinuria and glomerular hyperfiltration.
  
  
  METHODS
  Kidney biopsies from 11 non-diabetic obese with proteinuria and 14 non-diabetic lean patients with a creatinine clearance above 50 ml/min and with mild or no interstitial fibrosis were retrospectively analyzed using morphometric methods. The cross-sectional area of the proximal tubular epithelium and lumen, the volume of the glomerular tuft and of Bowman's space and the nuclei number per tubular profile were estimated.
  
  
  RESULTS
  Creatinine clearance was higher in the obese than in the lean group (P=0.03). Proteinuria was similarly increased in both groups. Compared to the lean group, the obese group displayed a 104% higher glomerular tuft volume (P=0.001), a 94% higher Bowman's space volume (P=0.003), a 33% higher cross-sectional area of the proximal tubular epithelium (P=0.02) and a 54% higher cross-sectional area of the proximal tubular lumen (P=0.01). The nuclei number per proximal tubular profile was similar in both groups, suggesting that the increase in tubular volume is due to hypertrophy and not to hyperplasia.
  
  
  CONCLUSIONS
  Obesity-related glomerular hyperfiltration is associated with proximal tubular epithelial hypertrophy and increased glomerular and tubular urinary space volume in subjects with proteinuria. The expanded glomerular and urinary space is probably a direct consequence of glomerular hyperfiltration. These effects may be involved in the pathogenesis of obesity-related renal disease.
authors.affiliation: Department of Pathology, Rabin Medical Center, Petah Tikva, Israel ; Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Ana
authors.initials: A
authors.lastname: Tobar
authors.forename: Yaacov
authors.initials: Y
authors.lastname: Ori
authors.forename: Sydney
authors.initials: S
authors.lastname: Benchetrit
authors.forename: Gai
authors.initials: G
authors.lastname: Milo
authors.forename: Michal
authors.initials: M
authors.lastname: Herman-Edelstein
authors.forename: Boris
authors.initials: B
authors.lastname: Zingerman
authors.forename: Netta
authors.initials: N
authors.lastname: Lev
authors.forename: Uzi
authors.initials: U
authors.lastname: Gafter
authors.forename: Avry
authors.initials: A
authors.lastname: Chagnac
mesh_terms: D000328:Adult; D004848:Epithelium / Q000473:pathology; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D006965:Hyperplasia / Q000473:pathology; D006984:Hypertrophy / Q000473:pathology*; D007678:Kidney Glomerulus / Q000473:pathology*; D007687:Kidney Tubules, Proximal / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000473:pathology*; D011507:Proteinuria / Q000473:pathology*; D012189:Retrospective Studies